Process for aromatization of olefin hydrocarbons

ABSTRACT

A process for the aromatization of olefin hydrocarbons at temperatures ranging from about 300*-800* C. and pressures ranging from about atmospheric to about 150 psi, by contact with catalyst composites of new and novel forms of chrysotile, improved in many of its physical and chemical characteristics as contrasted with previous species, and Group VIB or Group VIII transition metals.

United States Patent Eberly, Jr. [4 1 Aug. 22, 1972 [54] PROCESS FORAROMATIZATION OF 3,254,023 5/ 1966 Miale et a1 ..208/120 OLEFINHYDROCARBONS OTHER PUBLICATIONS [72] Inventor: Paul E. Eberly, Jr., 9440Ventura Dr., Baton Rouge, La. 70815 gg ggstracts, 23 {323 1 23 W?)- em.stracts, o. p. 70( [22] 1970 Chem. Abstracts, Vol. 53, 1959, p. 7712(g).[21] Appl. No.: 68,393

Primary ExaminerDelbert E. Gantz Assistant Examiner-J. Nelson 52 US. Cl...260/673.5 208/134, 252/455 i51i Int. Cl ..f ..C07c /26 gmmekpearlmanand Schlage and Llewellyn [58] Field of Search ..260/673.5, 673;208/134;

2 4 [57] ABSTRACT References Cited A process for the aromatization ofolefin hydrocar- UNITED STATES PATENTS bons at temperatures ranging fromabout 300800 C. and pressures ranging from about atmospheric to2,962,536 11/1960 Pitts ..260/673.5 b t 150 psi, by contact withcatalyst composites of 2,445,345 7/1948 Byms ..208/134 ew and novelforms of chrysotile, improved in many zetterholnt of its and chemicalcharacteristics as con, 3,317,438 5/1967 Engebretson ,.252/455 wastedwith previous species and Group VIB or 3,215,494 1 H1965 Hemstock ..23/110 Group v1 transition metals 2,640,756 6/1953 Wills ..23/111 3,580,9605/1971 Keen etal ..260/683.3 10 Claims, 1 Drawing Figure I I l lCHRYSOTILE SYNTHESIS AT 250 W.

11.1 2 E 2oo 5,

FLAK I TUBES v o l l l l |.o 1.25 1.5 1.75 2.0 2.5 PH (10) (12.5) (l3)3.5) 4) PATENTEDaunzz m2 CHRYSOTILE SYNTHESIS AT 250C.

FLAKES l TUBES IOO 1.5 L75 2.0 02.5) (l3) 03.5) NOgO/SiOg INVENTOR. PAULE. EBERL. Y

PROCESS FOR AROMATIZATION OF OLEFIN HYDROCARBONS Certain forms oflayered complex metal silicates are formed of sheets of paired layers ofSi O or serpentine, fused together with layers of metal chemicallycombined with hydroxyl ions. Illustrative of such naturally occurringmaterials which have common morphological and structural characteristicsare chrysotile, Mg (OH) Si O garnierite, Ni (Ol-l) Si O metahalloysite,A1 (Ol-l) Si O and kaolinite, A1 (OH) i O Synthetic complex metalsilicates of this character have been formed, these materials generallyretaining their high stability while having a higher degree ofdispersability, purity and homogeneity than those products found innature. These synthetic materials, particularly the pure materials, arethus useful as filtering mediums, absorbents, fillers and the like.Because of their high stability to heat, they are also use ful in theproduction of high temperature or flame resistant fabrics, and can beused in woven and nonwoven fabrics.

Asbestos is a naturally-occurring complex metal silicate of thischaracter. The term, commonly used to identify a material of a fibroustextile nature capable of being woven into a fabric, is morespecifically used to identify a variety of serpentines calledchrysotile, ideally Mg (OH) Si O supra, a species of layered complexmetal silicate. Though the structure can differ in chemical compositionto some extent due to the presence of impurities, thisnaturally-occurring material as other forms of chrysotile is aserpentine of type formed of sheets of paired layers of Si O fusedtogether with layers of metal, in this instance magnesium, chemicallycombined with hydroxyl ions. Investigations have been made of theproperties of these forms of complex metal silicates, and it has beenreported, e.g., that natural chrysotile has the configuration of hollowtubes or cylindrical fibrils with an averageKolloid-Zeitschrift,diameter of 200 to 250 A. (Angstrom units) and anaverage innerdiameter of to 50 A. As reported in the Encyclopedia ofChemical Technology, Second Edition, Volume 2, p. 738 (IntersciencePublishers), naturally-occurring chrysotiles typically have surfaceareas varying from 4 to 12 square meters per gram (m /g) though byadditional fibrilization the surface areas can be increased to 30 to 50m /g. Noll et a] have reported [(Kollid-Zeitschrift, Volume 157 [1],pages 1 to 11)] that synthetic chrysotile, Mg (OH) Si- O can be preparedhaving surface areas ranging as high as 110 m lg (BET Method). Noll etal have also reported [Beitrage zur Minralogie und Petrographie, Volume7, 1960, pages 232-241] synthetic nickel and cobalt substituted forms ofchrysotile-viz., garnierite, Ni (OH) Si O and Co (OH) Si O with surfaceareas ranging as high as 125 m /g and 190 m lg (BET Method),respectively. Little has been reported in regard to other forms ofchrysotile.

Chrysotiles have in the past been used as support materials, or caniers,for oxidation catalysts such as platinum supported on natural chrysotilefor use in the conversion of sulfur dioxide to sulfur trioxide. Despitethe apparent advantages offered by the extremely high thermal stabilityof this class of complex metal silicate, these materials, insofar as isknown, have never been used except as catalyst supports. A reason forthis, perhaps, is because, in their natural state, little if anycatalytic activity is shown. Moreover, though purer and morecatalytically interesting forms have been prepared synthetically overmany years, these materials yet remain little more than a matter ofacademic interest. Perhaps this is due in part to the extreme difficultyof preparing even minute amounts of these materials for experimentation.

Until now, synthesis of layered complex metal silicates, highlypreferred of which are the chrysotiles, has only been possible underhydrothennal conditions at relatively high temperatures and extremepressures. Generally, temperatures on the order of 350 C. to 600 C., andhigher, and pressures on the order of 13,000 psi (pounds per square inchabsolute) to 23,000 psi, and higher, have been employed to produce thesematerials. Such extreme conditions, of course, are not conducive tocommercial or large-scale operations, and though the purity and qualityof these materials over the natural products have been improved toprovide some advantages, the properties nonetheless did not appear ofparticular interest for use of these materials as catalysts. In largepart, this is probably due to the relatively limited number ofinteresting specimens found in nature, the only major source of supply,to the low surface areas observed in the naturally-occurring forms ofthese materials, and to the only relatively modest gains made insynthesis even of the few of these materials which have beensynthetically produced.

Nonetheless, it is the primary objective of the present invention toobviate these and other prior art difficulties.

A particular object is to provide a new and improved process forproduction of these layered complex metal silicates, or silicates formedof sheets of paired layers of Si O or serpentine, fused together withlayers of certain types of metal, or metals, chemically combined withhydroxyl ions.

A specific object is to provide such process which can be operated atlow severity conditions, i.e., at temperatures and pressuresconsiderably lower than heretofore possible, which process is capable ofproducing complex metal silicates resembling, or closely resembling, thechemical or physical composition, or both, of those found in nature aswell as a spectrum of new and novel complex metal silicates which differin chemical or physical composition, or both, from those found innature.

Another object is to provide complex metal silicate and chrysotilecompositions which differ in one or more of their chemical or physicalcharacteristics, or both, from those compositions found in nature, orheretofore synthetically produced.

A further object is to provide complex metal silicates and chrysotileswhich differ in one or more of their chemical or physicalcharacteristics, or both, for direct or indirect use as catalysts, orcatalytic agents, for use in hydrocarbon conversion reactions.

In addition to the many known usages of the layered complex metalsilicates, supra, and the advantages offered by synthesis of thesematerials with greater adsorption and absorption capacities, and in highpurity state, the present compositions can be used directly or modifiedby known techniques for use in hydrocarbon conversion reactions forimproving the octane number of gasoline or converting relatively heavyhydrocarbons to light, lower boiling hydrocarbons, and includingconverting hydrocarbons by hydrogenation or dehydrogenation to saturateor unsaturate, in whole or in part, various species of molecularhydrocarbons. Among such hydrocarbon conversion processes arearomatization, isomerization, hydroisomerization, cracking,hydrocracking, polymerization, alkylation, dealkylation, hydrogenation,dehydrogenation, desulfurization, denitrogenation, and reforming.

It has now been found that layered complex metal silicates, particularlychrysotiles, of shape ranging from very thick wall tubes (substantiallyrods in character) through moderately thick wall tubes, thick wall tubesthrough thin wall tubes, and thin wall tubes through flakes can besynthetically prepared from soluble forms of silica, and certain metalsor their oxides and hydroxides in alkaline medium, in criticalconcentration, at moderate temperatures and pressures. The layeredcomplex metal silicates, including chrysotiles, formed in accordancewith the present inventive process, and certain of the high surface areacompositions of the present invention, are of crystalline structuredefined chemically by repeating'units represented by the followingstructural formula:

u) [(IX)M(X\) xmwnnwmisnotwino where M and M are selected frommonovalent and mu]- tivalent metal cations, of valence ranging from 1 to7, having an effective ionic radius [Goldschmidt radius, Effective Radiiof Atoms and Ions from Crystal Structure, Page 108, Langes Handbook ofChemistry, Tenth Edition, Handbook Publishers, Inc., Sandusky, Ohio]ranging from about 0.5 to about 1 A., and preferably from about 0.57 toabout 0.91 A., x is a number ranging from to 1, this number expressingthe atomic fraction of the metal s M and M, a is the valence of M, b isthe valence of M, n is a number equal in value to that defined by theratio 6/[a(1x) +bx], and w is a number ranging from 0 to 4. Some speciesof these complex metal silicates have been found to exist in nature, andsome species have been synthetically produced. Some species differchemically from those found in nature, or those heretofore syntheticallyproduced, and others, though chemically similar, possess differentphysical properties.

Illustrative of this type of complex silicate, in any event, is the formof serpentine known as chrysotile the dehydrated form of which has theidealized structural formula Mg (OI-I) Si O The formula is idealized inthe sense that chrysotiles, as other minerals, rarely, if ever, appearin nature in pure form but contain very small amounts of impurities suchas iron, aluminum, and the like, substituted for magnesium, andoccasionally for silicon. Chrysotile is a mineral derived from multiplelayers of Si O or serpentine, condensed with Mg(OH) or brucite layers,this material existing in nature as cylindrical shaped rods or thicktubes. The naturally-occurring mineral antigorite is also illustrativeof such complex silicate having the idealized formula Mg (OH) Si O Innature, this material is also constituted of Si O or serpentine,condensed with layers of Mg(OI-I) or brucite. This material, however, is

found in nature in the form of plates of undulating shape. Orthoserpentine, Mg (OH) Si- O a six-layer serpentine, is also found innature, as is lizardite, Mg (OI-I) Si O which is a one-layer serpentine.Both of these materials are found in the form of plates. Garnierite, anickel substituted form of layered complex silicate, Ni (OH) Si O isfound in nature in the form of tubes. Synthetic garnierite has also beenprepared by prior art workers, nickel having been substituted formagnesium in conventional synthetic chrysotile formulations. Cobaltchrysotile, Co (OH) Si O has been prepared in similar manner. Insofar asknown, however, attempts to prepare other useful forms of syntheticchrysotiles have failed.

The process of this invention can be employed not only to producecomplex metal silicates of known chemical composition, but also complexmetal silicates of new and novel chemical composition. It can also beused to produce both old and new chemical compositions with new,different, and unique physical properties, particularly as regards highsurface area compositions.

Chrysotiles of known chemical composition are thus included in theforegoing formula (I), but even these compositions can be produced withentirely different physical properties, especially as regards surfaceareas. Essentially pure forms of chrysotile, defined in the foregoingformula as those species wherein x does not exceed about 0.03 andpreferably about 0.01, are thus magnesium chrysotile Mga(0H) Si O withsurface areas of above about m /g, nickel chrysotile, Ni (OI-I) Si Owith surface areas of above about m lg, and cobalt chrysotile, Co (OH)Si O with surface areas above about 190 m /g, the maximum surface areasachieved by prior art practice, can thus be produced pursuant to thepractice of this invention. Other forms of chrysotile, included withinthe scope of this formula, can also be produced pursuant to thisinvention but with surface areas exceeding 1 l0 m lg, the maximumsurface area heretofore achieved by prior practice (exclusive of thenickel and cobalt chrysotile species). Preferred forms of these highsurface area species are those in the form of thin wall tubes of surfacearea ranging about m /g to about 250 m /g, preferably from about m lg toabout 200 m/ g, and those in the form of thin flakes of surface arearanging from about 250 m lgto about 600 m /g, and higher, preferablyfrom about 250 m /g to about 450 mlg.

Pursuant to the practice of the present process, cornpositionscan beprepared which differ in their chemical structure from heretoforeexisting compositions in that they contain two or more metals insignificant concentration within the crystalline structure, and include,particularly, such compositions of high surface areas. These newcompositions are of crystalline structure defined by repeating unitsrepresented by the following structural formula:

wherein M and M are metal cations having an effective ionic radius(Goldschmidt) ranging from about 0.5 to about 1 A., a expresses thevalence of M and is equal to 2, b expresses the valence of M and is aninteger ranging from 1 to 7, and preferably is an integer ranging from 2to 4, x is a number ranging from 0.01 to 0.50, preferably from 0.03 to0.20, and n is a number ranging from 2.5 to 3.3, and preferably from 2.7to 3.0. w is a number ranging from to 4. Exemplary of such compounds are(0.2 Ni 0.8 Mg) (OI-I) Si O wI-I O; (0.1 Al 0.9 Mg) (OH ).,Si O wI-I 0;(0.05 W 0.95 Ni Si O wH O; and (0.1 Li 0.9 Mg) (OI-I) Si O wH O.

In these formulas M and M can thus be the same or different metals, andthese can be of the same or different valence. The complex metalsilicates can thus contain essentially one metal, or can contain two ormore different metals in varying concentrations. In formula (I) M and Mcan be monovalent or multivalent metals of valence ranging from 1 to 7,while in formula (II) M is a divalent metal. The valence of M can rangefrom 1 to 7. M of the formulas can also represent more than onemonovalent ormultivalent metal, though substantially bimetalliccompositions are generally preferred. The cationic form of the metal ofthe crystal must have an effective ionic radius substantially within theranges described. Illustrative of metals utilized in acceptable cationicform, which can be selected from the Periodic Table of the Elements (E.H. Sargent & Company, copyright 1962 Dyna Slide Co.), are Group IAmetals such as lithium, Group [B metals such as copper, Group IIA metalssuch as magnesium, Group IIB metals such as zinc, Group lIIB metals suchas scandium, Group IIIA metals such as aluminum and gallium, Group IVBmetals such as titanium and zirconium, Group VB metals such as vanadium,Group VIB metals such as chromium, molybdenum and tungsten, Group VIIBmetals such as manganese and Group VIII metals such as iron, cobalt,nickel, palladium and platinum.

Preferred metals from these classes are magnesium, nickel, cobalt,chromium, molybdenum, tungsten, palladium, platinum and aluminum.Magnesium is preferred because of the relative ease of formation of thecomplex magnesium silicates which are useful as catalysts, and suchsilicates are quite useful as support materials, Pursuant to the processof this invention, other complex metal silicates are formed bysubstitution of other metal ions for the magnesium. Nickel and cobaltare also preferred metals with known catalytic properties, and can bereadily substituted for magnesium, in whole or in part to provide highlyactive hydrogenation components in formation of fuels processingcatalysts. Chromium is found highly suitable for formation of othercomplex metal silicates of the type herein described, and can be used toproduce aromatization catalysts of good quality for use in fuelsprocesses. Molybdenum is found useful, especially for the production ofhydrodesulfurization and reforming catalysts. Tungsten and palladium areuseful for formation of hydrocracking catalysts. Platinum is useful informing reforming catalysts and aluminum for use in the production ofcatalytic cracking catalysts. In general, the synthetic chrysotiles ofthis invention provide a means of maintaining a metal in dispersed formon a silica surface to provide greater activity, this being contrastedwith the addition of metals to such preformed support materials whichleaves something to be desired in maintaining this high state ofdispersion.

Complex metal silicates of these types can be synthetically prepared inhydrated form in very high yields from solution or gels, and thenconverted to dehydrated form by subjection to heat, as desired. Thevcomplex metal silicates are prepared by reacting a metal cation sourcewith a silica source in proportions approximating the stoichiometriccomplex metal silicate composition, in an alkaline medium of pH rangingfrom about 10, and higher, and preferably at pH ranging from about 12 toabout 14, at moderate temperatures and pressures. Suitably, the reactionis conducted at temperatures ranging below 300 C., preferably attemperatures ranging from about 200 C. to about 275 C. Lowertemperatures can be used but the reaction proceeds quite slowly.Pressures in many systems are suitably autogeneous, i.e., maintained atthe vapor pressure of the liquid solvent at the temperature ofoperation. This is especially true of aqueous mediums, these mediumsbeing especially preferred. Pressures as high as 12,000 psi, and higher,can be employed, but generally it is commercially unfeasible to operateat pressures above about 1000 psi. Preferably, pressures ranging fromabout 200 psi to about 1000 psi, and more preferably pressures rangingfrom about 400 psi to about 800 psi are maintained upon the reactionsystem. Reaction time ranges generally from about 0.5 to about 72 hours,and preferably from about 4 to about 24 hours.

The compositions of the present invention encompass: (a) layered complexmetal silicates defined by Formula (I) where the surface area of thecomposition ranges above about m lg, except as regards nickelchrysotile, Ni (Ol-I) Si O and cobalt chrysotile, Co (OH) Si O butencompasses these latter species wherein the surface areas range aboveabout m /g and m /g (BET Method), respectively; and (b) layered complexmetal silicates defined by Formula (II), the higher surface areacompositions being especially preferred. The most preferred compositionsof the present invention, because they are admirably suitable for director indirect use as hydrocarbon conversion catalysts or catalystsupports, are the chrysotiles. For purposes of this invention,chrysotiles are those compositions defined in Formula (I) and Formula(II) wherein the Si O or serpentine layers of the repeating unit whichform the crystals, areof smaller length or diameter than the associatedmetal hydroxide layers to which the serpentine layers are adjoined. Thischaracteristic structure is distinguishable from other layered complexmetal silicates, and other crystalline substances, by X-ray diffractionpatterns whether the crystal structures exist as tubes or flakes.

X-ray powder diffraction data for the two physically different forms ofchrysotile are as given below:

X-Ray Diffraction Patterns for Chrysotile sizllssil...

In obtaining the X-ray powder diffraction pattern, standard procedureswere employed. The radiation source was the K-alpha doublet for copper.A Geiger counter spectrometer with a strip chart pen recorder was usedin recording the data. The peak heights 1, and the positions as afunction of 2 0, where is the Bragg angle, were read from thespectrometer chart. From these, the relative intensities I wereobserved. Also, the interplanar spacing, d, in Angstrom Units,corresponding to the recorded lines, were determined by reference tostandard tables. In the above table, the more significant interplanarspacings, i.e., d values, for chrysotile tubes and flakes respectively,are given. The relative intensities of the lines are expressed as s(strong), m (medium) and w (weak).

In chrysotile it is thus known that the mineral is formed of pairedserpentine and brucite layers which do not match, and hence the crystalis strained. Consequently, this gives rise to different physical formsand shapes inasmuch as relief from the strain is gained by a curl of thecrystal along its long axis so that chrysotile exists in nature ascylindrical shaped rods or thick wall tubes. The thick wall tubularstructure has been observed in synthetic forms of chrysotile In thepresent process, the complex metal silicates are also formed as thickwall tubes, thin wall tubes, curls or flakes, as desired, from gels aspaired layers of different sizes. Layers of silicon-oxygen sheets arecombined with layers of hydroxyl groups cemented to the silicon-oxygensheets by metal cations. Each of the repeating units, considering forconvenience the anhydrous form, is thus formed of a layer of serpentine,or SL 0 and an adjacent larger sized layer of metal chemically combinedwith hydroxyl ions, or [(1 x)M xll'f ,,(OH),, to which the former isfused. The paired, fused metal-hydroxyl ions and serpentine layers areheld together by very strong forces of attraction, while the repeatingunits of paired layers per se are held together by weaker forces ofattraction. A serpentine or Si O layer is formed of a sheet of linkedSiO, tetrahedra, three oxygen atoms of each SiO, being shared withadjacent SiO, tetrahedra, in the same layer. The vertices of all thetetrahedra point in the same direction, or outwardly for a rod or tubestri ture. In the metal-hydroxyl layer or l x)M xM"],,(OH)., layer,one-third of the oxygen atoms are oxygen ions [0' ]which are shared withsilica tetrahedra of the adjacent serpentine or Si O layer. Theremaining oxygen atoms are hydroxyl groups, and these at: associatedonly with M or M cations. Thus, the M or M cations are surrounded by sixions, four hydroxyl groups, or ions, and two oxygen ions in a case wherethe metal is a divalent cation such as magnesium.

These forms of layered complex metal silicates can thus be logicallyconsidered as chrysotiles, or substituted chrysotiles, since theypossess thechrysotile W O O Tier 1 is constituted entirely of oxygenions. Tier 2, constituting the tetrahedral cation position, isessentially constituted of silicon ions. Tier 3 is constituted of bothoxygen and hydroxyl ions--viz., two oxygen ions and a hydroxyl ion. Tier4, which constitutes the octahedral cation position, is constituted of amonovalent or multivalent metal cation M or M. This is the primarycation site for substigtion of the various metals represented by M and Minto the chrysotile structure. Where only magnesium is contained in theoctahedral cation position, the chemical structure is that ofchrysotile; and where nickel or cobalt is wholly substituted formagnesium, the chemical structure is also that heretofore producedsynthetically and known as nickel chrysotile (or garnierite) and cobaltchrysotile. Tier 5 is constituted entirely of hydroxyl ions. Theserpentine or Si O layer is constituted of those tiers of ions rangingfrom 1 through 3, and the metal-hydroxyl ion layer is constituted ofthose tiers of ions ranging from 3 through 5. Two of the ions of Tier 3are shared between the serpentine layer and the metal-hydroxyl ionlayer, while the third ion is more identifiable with the metal-hydroxylion layer. In the repeating unit Tier 1 contains 3 oxygen atoms, Tier 2contains 2 silicon.

atoms, Tier 3 contains 2 oxygen atoms and 1 hydroxyl ion, Tier 4contains 3 magnesium ions and Tier 5 contains 3 hydroxyl ions. While itis not apparent from accepted Pauling notation, the two layers are notof the same dimension, the metal-hydroxyl ion layer being of greaterlength than the serpentine layer so that there is a misfit of the twolayers, and hence a strain between the paired layers which form arepeating unit.

The metal-hydroxyl ion layer of a repeating unit is of greater area (andlength at least in one dimension) than an adjoining serpentine layer,the misfit between the two layers producing a stress-strain relationshipwhich causes the layers to curve in a direction such that the concaveside of the metal-hydroxyl ion layer adjoins the convex side of theserpentine layer. When the chrysotile is in tubular shape, this meansthat the structure is of coil shape, or formed of a series ofconcentriclike paired layers of the repeating units and the serpentinelayer is the smaller diameter member of the paired ay s The misfitbetween the paired layers in conjunction with the pH of the reactionmedium at the time the crystals are formed is believed to give rise, atleast in part, to the present inventive process. Pursuant to thepractice of the present inventive process, in any event, it has beenfound that a definite relationship exists between the pH of the alkalinemedium and the, nature and physical form of the crystalline materialswhich are formed, as well as with respect to the temperature andpressure at which the reactions can be conducted. By conducting thereactions at a pH of above about 10, and preferably at from about 12 to14, it has been found that the reactions can be conducted atconsiderably lower temperatures and pressures than heretofore believedpossible. This not only makes large scale commercial operation feasiblebut, additionally, provides a means of product quality control. It hasthus been found that pH can be used to provide complex metal silicatesof the types described in physical forms and shapes ranging generallyfrom cylindrical shaped rods through thick wall tubes, from thick walltubes through thin wall tubes, and from thin wall tubes through flakes.On the one hand, where the chemical species is known to exist, some ofthe physical forms are found in nature, or have heretofore beensynthetically produced. Others differ physically from the natural forms,or forms heretofore synthetically produced. On the other hand, some ofthese materials are chemically as well as physically different forms.For example, chrysotile, Mg (Ol-l) Si O is found in nature in the formof rods and thick wall tubes of low surface area. This material has alsobeen heretofore produced synthetically as thick wall tubes with maximumsurface area of 110 m /g. Thin wall tubes of higher surface areas areunknown. Other minerals having the same chemical structure as chrysotileare known to exist in nature, e.g., antigorite. It exists in nature asplatelets of undulating shape, and generally possesses a very lowsurface area. Gamierite, Ni (OH) Si O and a cobalt form of chrysotile,Co (OH) Si O have been synthetically produced, but as specimens ofsurface area ranging as high as 125 m /g and 190 m lg, respectively. III A feature of this process is that by judicious selection of pH,surface areas can be improved considerably, generally at least two-foldand ranging as high as almost ten-fold over the corresponding naturalproducts where they exist. The surface areas of these materials can thusbe controlled within conventional ranges, e.g., in the case of magnesiumchrysotile up to about 110 m /g, or can be increased above 1 m g.Preferably, tubes can be formed which have surface areas within therange of from about 150 m /g to about 250 m lg, and higher, and morepreferably within the range of from about 160 m /g to about 200 m /g(B.E.T. method; absorption of N at its normal boiling point).Preferably, flakes can be formed with surface areas ranging from about250 m /g to about 600 m /g, and more preferably from about 250 m lg toabout 450 m lg. The nickel form of chrysotile, Ni (OH) Si O and thecobalt form of chrysotile, Co (OH) Si O in the form of tubes and flakes,can be produced with surface areas greater than 125 m /g and 190 m /g,respectively, and preferably within the higher range of limitsdescribed. It is found that at different pH levels the character of thecrystals can be controlled so that a given chemical specimen can beformed in the shape of rods, thick wall tubes, curls, or thin flakes andthat surface areas can be controlled during the transition, surface areaincreasing as pH is lowered to favor, directionally, the production ofrods through thick wall tubes, thick wall tubes through thin wall tubes,and thin wall tubes through flakes.

In general, in the formation of a species of chrysotiles at controlledconditions, as pH is lowered the tube walls get thinner, and the thinwall tubes generally yield surface areas no greater than about 200 rn /gto about 250 m g. As pH is further lowered to obtain higher surfaceareas, the thin wall tubes form curls (or malformed tubes), and thenbreak apart and form higher surface area flakes, the walls of which,directionally,

also become thinner as pH is lowered. Thus, at constant temperature andpressure, specimens of definite character are formed at a selected pH.The actual transition points vary to some extent dependent largely uponthe nature of the metal, or metals, used in formation of the complexmetal silicate. The thickness of the walls of the tubes can thus bedirectly controlled by the selected pH. Thin wall tubes of only a fewpaired layers,

e.g., 4 to 8 in thickness, can be formed. Such tubs rang- It) ing fromabout 20 A. to about A., and preferably from about 28 A. to about 45 A.,in thickness provide tubes of far greater inside diameter than occurs inthe corresponding natural products, providing far greater adsorptionspace and accessibility for catalytic contact by reactant materials uponcatalytic surfaces. For example, in sharp contrast tonaturally-occurring magnesium chrysotile which exists in a cylindricalor rodlike form or in a thick wall tubular form having an inner diameterranging from about 20 A. to 50 A., high surface area chrysotilecompositions of this invention exist as tubes having inner diametersabove 50 A., preferably from about 60 A. to about A., and higher. Theaccessibility and high concentration of large pore openings which existin these materials are quite important in considering the availabilityof surface areas for catalytic purposes. At surface areas above about250 m /g the chrysotile compositions of this invention are usuallyformed as relatively thin flakes. The thin flakes, because of theirultra-high surface areas, are the most preferred compositions for use inmost hydrocarbon conversion reactions. I

As suggested, as the pH is further decreased, at the selectedconditions, the tubes begin to curl and then break apart to fonn thinflakes of very high surface area. The flakes range in thickness fromabout 15 to about 50 A., and preferably from about 20 to about 30 A.

It is feasible, at these low severity process conditions, to synthesizenew and novel complex metal silicates from solutions containing reactivesilicates, and reactive forms of the desired metal, e. g., solublesalts, or 0x ides and hydroxides. The reactants are combined in alkalinemedium at moderate temperature and pressure. The complex metal silicatesare formed in two steps. In a first step, a synthesis gel is formed bycoprecipitation of the metal oxides or hydroxides with hydrous silicagel in alkaline medium. In a second step, the gel is heated at fromabout 200 C. to about 350 C., and preferably from about 250 C. to about275 C., so that the chrysotile product is crystallized from thesynthesis gel with rejection of excess water and soluble salts which areremoved by filtration and washing. At the time of formation of thesynthesis gel, the composition of the metal hydroxide layer of thecrystal is fixed by selectin g the concentration of metals to vary theratios of M/M, as desired. The structures are useful as catalysts, orcan be further modified after initial formation, as desired, by cationexchange, as with ammonia and selected metal cations, or by impregnationwith metal anions or cations, or both, or by a combination of ionexchange and impregnation. I I I The process improvements wherebypreviously existing or naturally-occurring complex metal silicates, aswell as new and novel forms of complex metal silicates, can be made isefiected by the use of highly alkaline mediums, of critical pH. Highalkalinity causes the reaction to proceed at substantially milderconditions than heretofore believed possible. This favorable effect,which makes it generally unnecessary to conduct the reactions at thehigher conventional temperatures and pressures, is not completelyunderstood. The highly alkaline medium is employed to cause breakage ofthe silicon oxygen bonds, or depolymerization of the SiC) components, sothat the latter become more freely migratory within the solution or geleven at relatively low temperatures and pressures. In any event, it isfound that alkali concentration can be varied, as desired, in thereaction system to provide a variety of complex metal silicates, someresembling products heretofore found in nature or produced by othersynthesis techniques, either in their chemical or physicalcharacteristics, or both, and many products heretofore unknown asregards either their chemical or physical characteristics, or both.

The nature of the reaction by virtue of which pH can be used to controlthe physical forms of the chrysotiles produced is thus not entirelyunderstood, but it would appear that the strain produced by the misfitof the unequal sized serpentine, Si O and the larger metalhydroxyl ionlayers is in part responsible for this phenomenon. Thus, at the selectedlow severity conditions, the strain is greatest on the layers fartherestaway from the equilibrium diameter. At a given intermediate pH, crystalsassume the form of thin wall multilayer structures of only a few layersthickness. These crystals are of high surface area and possessrelatively large internal openings. At higher pH, the walls are thick,or the structure is even rod-like. At lower pH, the strain between thepaired layers causes the tube to break apart to form high surface area,thin flakes. The use, or substitution, of metal cations of differentsize into the octahedral cation position, which is believed to be theprimary cation site for substitutions, thus further alters thestress-strain relationship between the forming crystals. Hence, it wouldnot be expected that single set of parameters could be used to definethe transition points, or zones, for the crystals of all of thedifferent metals which can be substituted at the primary cation sites.It is found generally, however, that cations which most closely approachin size the effective ionic radius of magnesium are most readilysubstituted, and in highest concentration. It also appears that the sizeof the larger metal hydroxide layer of a crystal structure is directlyrelated to the size of the cation substituted for magnesium and hencethe stress-strain relationship altered so as to effect the curvature ofthe structure caused by the misfit between the larger metal hydroxidelayer and the adjacent smaller serpentine layer. Whatever theexplanation, however, the technique is admirably suitable for producingwhole new families of high surface area crystals, and even families ofcrystalschernically different from those found in nature, or thoseheretofore synthetically produced.

Various alkaline materials can be used in the practice of thisinvention, providing they possess sufficient alkalinity to raise thereaction medium to the necessary pH, do not react to a significantextent with the forming complex metal silicates, with the intermediatematerials, precipitate the silica, or decompose to gaseous products.Most preferred of these alkaline materials, for these reasons, are thealkali metal and alkaline earth metal hydroxides, exemplary of which areGroup lA metal hydroxides such as sodium hydroxide, potassium hydroxide,cesium hydroxide and the like, and Group "A metal hydroxides such asbarium hydroxide, strontium hydroxide and the like. A satisfactory GrouplllA metal hydroxide is thallium hydroxide. Various Various sources ofsilica can be employed present process, these including essentially anyof the conventional, widely used silica sources such as silica per se,diatomaceous earths, silica hydrogel, silica hydrosol, alkali metalsilicates, e.g., sodium silicate, and the like. Particularly preferredsources of silicates are silica sol, silica gel, and sodium silicatesolution Warmest H Virtually any form of compound which is sufficientlysoluble and compatible with the reaction mixture, which contains thedesired metal, can be used as a source of the metal. Soluble salts ofthe metals, or mixtures of such salts, e.g., halides, sulfides,sulfates, nitrates, carbonates, acetates, phosphates, or the like, canbe used to supply the desired metal, or metals, in formation of thecomplex metal silicates. Exemplary of such salts are lithium chloride,lithium bromide, cupric chloride, cupric sulfate, magnesium chloride,magnesium bromide, magnesium sulfate, magnesium sulfide, zinc acetate,zinc chloride, zinc bromide, scandium bromide, scandium sulfate,aluminum chloride, aluminum bromide, aluminum acetate, aluminum nitrate,aluminum phosphate, aluminum sulfate, gallium nitrate, gallium sulfate,titanium bromide, titanium trichloride, titanium tetrachloride, titaniumoxydichloride, zirconium dibromide, zirconium sulfate, zirconyl bromide,vanadium bromide, vanadium trichloride, vanadyl sulfate, chromicacetate, chromic chloride, chromic nitrate, chromic sulfate, molybdenumoxydibromide, tungsten trisulfide, manganous sulfate, ferric chloride,ferrous chloride, ferrous sulfate, cobaltous nitrate, cobaltous sulfate,nickel chloride, nickel bromide, palladium chloride, palladium sulfate,platinic tetrachloride, and the like. Many hydroxides, oxides, oroxygenated anions of these various metals can also be employed, andthese are particularly useful where it is desirable to increase the pHof the solution over and above that practical by a relatively weak base.Illustrative of such compounds are magnesium hydroxide, magnesium oxide,sodium tungstate,

sodium molybdate, sodium chromate, sodium vanadate and the like. Othermetal sources can also be employed, e.g., chloroplatinic acid,chloropalladous acid The relative amounts metal sources are most easilydetermined by the stoichiometry of the desired product, though the useof exact stoichiometric amounts of these materials in a given reactionmixture is unnecessary. Typically, the sources of silica and metal areused in quantities sufficient to provide a reaction mixture having ametal, or mixture of metals (calculated as the oxide or oxides),relative to the silica (calculated as the oxide) in mole ratio rangingfrom about 1 to about 2, and preferably from about 1.4 to about 1.6.

The invention will be more fully understood by reference to thefollowing data, selected to demonstrate the more salient features of thenovel process for preparation of these complex metal silicates, new andnovel compositions, and the process of their use in various hydrocarbonconversion reactions.

A first series of runs are presented to demonstrate the manner in whichpl-l can be used to control the production of the complex metalsilicates. Chrysotile, Mg (Ol-l) Si O is first selected to illustratecomplex metal silicates of chemical type which, though found in natureand heretofore synthetically produced, can be nonetheless produced innew, different, and unique physical forms.

EXAMPLES 1ll In each of the runs tabulated in Table l, the silica sourcecomprises either colloidal silica sol, 150 A. particle size, sold underthe Dupont tradename as Ludox LS-30, or sodium metasilicate. The silicasource is added to an aqueous solution of a suitable magnesium source,i.e., a magnesium salt, in concentration of 50 parts by weight of thesalt in 100 parts by weight of water. In order to produce the desiredpH, to a solution or gel is then added various amounts of an alkalimetal hydroxide, from a solution made up of 60 parts by weight of thealkali metal hydroxide per 100 parts by weight of water, with stirringfor about 5 minutes at C. and atmospheric pressure. Typically, as isdemonstrated, the silica and magnesium sources are used in quantitiessufficient to provide a reaction mixture having a MgO/SiO mole ratioranging from about 1.0 to about 2.0, but preferably of about 1.5. The pHof the solution ranges from 10 to 14, as determined by the amount ofalkali metal hydroxide added.

The resultant mixtures are placed, in separate series of runs, in anautoclave heated at 250 C. at pressure of 570 psi. After a period of 24hours, the resultant insoluble products obtained in high yield,substantially stoichiometn'c, are cooled, filtered, washed with 10volumes of water to produce low sodium chloride levels, and dried at 120C. in an oven. All specimens are positively identified by X-raydiffraction data as chrysotile.

TABLEl Synthesis of Chrysotile Sur- Phy- Reuction Mixture Compositionsface sical Silica Mg MSO/ Ns,0/ H,Ol Area form of Ex. Source Source SiSiO, SiO,m'/g" composttions l LS-" MgCl, 1.5 2.5 42 72 Tubes 2 LS-30MgSO. L5 2.5 64 92 Tubes 3 LS-30 MgCl 2 2.5 44 73 Tubes 4 LS-30 MgCl, L5L5 42 249 Tubes 5 Meta- MgCl, 1.5 2.5 65 93 Tubes silicate 6 LS-30 MgCl,1.5 2.5 44 129 Tubes 7 LS-30 MgCl, 1.5 2.5 44 132 Tubes 8 LS-3O MgCl:1.5 1.5 42 228 Tubes 9 1.5-30 MgCl, 1.5 1.0 51 468 Flakes 10 155-30 MgCl1.5 1.0 51 444 Flakes $0,) 11 LS-30 MgCl 1.5 1.5 51 467 Flakes SiO,

a. Surface area, and all surface areas reported and claimed herein,determined by BET Method: N, adsorption at its normal boiling point.Shell Development Company, Simplified Method for the Rapid Determinationof Surface Area by Nitrogen Adsorption," Report No. S-9815R, May 3,1945.

b. Colloidal silica sol (150 A) particle size sold under the trade nameLudox LS-30."

0. Reaction temperature of 275C.

d. Reaction at 275C. for 48 hours.

e. KOH used as the alkali metal hydroxide.

A definite relationship is thus found to exist between the pH, orcaustic mole ratio, and the surface area of the chrysotile produced.These result, graphically shown by reference to the attached figure,show that exceptionally high chrysotile surface areas are produced whenalkali metal hydroxide is used in limited quantity to produce a reactionmixture having an alkali metal oxide-to-silica mole ratio below about 5t asprrssp ns in lsaafistatue Referring further to the figure, it isfound that long tubular shaped crystals with thick walls, openings ofrelatively small diameter, and low surface area are produced at Na OISiOratios ranging from about 2.5 to about 2.0. The wall thickness of suchcrystals thus ranges from about to about 50 A., the internal diameter ofthe openings from about 30 to about 60 A., and the surface area fromabout 70 to about m /g. At Na OISiO ratios between about 2.0 and 1.5,thin wall tubes with internal openings of relatively large diameters andhigh surface areas are formed. The wall thicknesses of these types oftubes thus range from about 50 to about 30 A., the internal diameter ofthe tubes from about 60 to about A., and the surface area from about 120to about 250 m /g. Within the range of Na O/SiO ratios beginning atabout 1.5, the thin wall tubes apparently break down to form porousflakes. Thus, at Na O/SiO ratios ranging about 1.5 and lower, thinflakes are formed. Such flakes range in thickness from about 30 to about20 A., and have surface areas which range from about 250 to about 600lan hish r- These data show that pH can be controlled to ameliorateprocess conditions, as well as to optimize the quality of the products.The process also makes it feasible to produce complex mixed metalsilicates, as demonstratedbythe following selected data.

EXAMPLE 12 A cobalt substituted chrysotile is prepared in the followingmanner: 50 parts by weight of Ludox LS-30 (described above) is addedwith stirring to a solution containing 9 parts by weight of CoCl -6H O,68.6 parts by weight of MgCl -l-l O and 150 parts by weight of water. Asolution consisting of 30 parts by weight of NaOH and 50 parts by weightof water is then added to the aforedescribed mixture and stirred at 25C. and atmospheric pressure for about 5 minutes. The resulting mixtureis then placed in an autoclave and heated to 250 C. for about 24 hours.The product is then cooled, washed and dried using the procedure givenwith reference to the foregoing examples. The product recovered, whichis in the physical form of tubes, is a substituted chrysotile(identified by X-ray diffraction) having about 10 percent of themagnesium cations replaced with cobalt cations and having a surface areaof ab 67 mt The following series of data, given in Table II, isillustrative of additional runs for the preparation of substitutedmixed-metal forms of chrysotiles. All specimens are positivelyidentified by X-ray diffraction data as chrysotile.

TABLE II.SUBSTITUTED CHRYSOTILES Reaction mixture composition ReactionPercent of Mg conditions, Surface replaced with Metal cation Total metalhours at area, Physical form of Example metal cation source Mg sourcecation/S10; NazO/SIO; HaQ/SIO: 250 C. M /g. compositions NiSO4 MgSOa1: 1. 5 58 16 260 Curls and flakes.

NiSOi I. 5 l. 25 58 24 338 Flakes. (loch-EH MgCl: 1. 5 2. 5 52 24 122Tubes. OoCla-GHaO MgCI: 1. 5 1. 25 63 24 408 Flakes FeClz-fiHzO MgCl2 1. 5 1. 5 52 24 398 MIlC1z-4H2O MgClz 1. 6 2. 5 52 66 88 Tubes.CUCIz-2H20 MgCl-z 1. 5 1. 5 47 24 311 Flakes. OrCh-GHZO MgClz 1. 5 2. 552 65 356 Do. ZnC12 MgClz 1.5 2. 5 47 24 166 Tubes.

Molar basis.

The present low severity process makes feasi I possible at temperaturessignificantly below those employed heretofore. For example, Nesterchuket al Zap Uses Mineralog Obshchestria 95 [1], 759 [1966]) and Roy et al(American Mineralogist 39, 957,975, [1954]) have reported the synthesisof chrysotile at temperatures ranging from about 350 to 600 C., atconventional hydrothermal conditions requiring a pressure ranging fromabout 13,000 psi to about 23,000 psi. In contrast, production ofchrysotile at 250 C., as described in the foregoing Example 12, requirespressures of only about 570 psi (vapor pressure of water at 250 C.), andwill readily permit the large-scale manufacture of such chrysotiles.AROMATIZATION Certain of the complex metal silicates can be used per soas catalysts, orcan be composited with various materials to formcatalysts useful in aromatization of olefinic hydrocarbons, whetherstraight chain or branched chain, monoolefinic or polyolefinic andwhether conjugated or unconjugated. For example, straight chain olefinscan be converted to aromatic compounds, e.g., as in the conversion ofhexene-l and heptene-l to benzene and toluene, respectively. While suchprocess can be used for the conversion of olefins to aromatics forchemical uses, it is particularly important in petroleum fuelsprocessing. This is so in that olefins have many undesirable propertiesin motor gasoline and can be converted to aromatics with higher octanenumber to producesuperior gasoline, while simultaneously eliminatingmaterials which contribute to gum formation and air pollution. Inaccordance with the present invention, however, higher octane numberproducts can be obtained and substantial portions of the olefiniccontent of feeds converted into desirable aromatics, without significantconversion to lighter hydrocarbons.

Olefinic hydrocarbons containing from about 6 to about 12 carbon atomsare preferred, and these are aromatized according to the presentinvention by contacting a suitable feedstock with the catalyst at lowpressures ranging, i.e., from about atmospheric to about 150 psi, andpreferably at from about atmospheric pressure to about 75 psi. An inertgas, e.g., nitrogen, helium, methane, or the like, or hydrogen can beemployed. Use of an inert gas offers certain advantages inasmuch astheir use forces the reaction to proceed to completion since hydrogen isa product of aromatization. However, in certain cases, catalystdeactivation may occur and use of a moderate hydrogen pressure is quitebeneficial to prevent catalyst activity decline.

Temperatures ranging from about 300 C. to about 800 C., preferably fromabout 450 C. to about 600 C.,- are used. High conversion of olefinichydrocarbons with good selectivity to aromatics are obt in d-7...--. ,7

In preparation of preferred types of aromatization catalysts atransition metal, or mixture of such metals,

is generally composited with a suitable base, as by impregnation of thebase or crystallization of the base with a suitable metal hydroxide. Thepreferred transition metals which are dispersed upon a suitable base areGroup VIII metals, illustrative of which is platinum, iridium,palladium, rhodium and including iron, cobalt and nickel. Group [Bmetals, preferably as their oxide, such as copper, silver and gold, canalso be composited with the Group VIII metals. Other metals, preferablyin the form of their oxides, can be impregnated or otherwise composited,either alone or in combination with the Group VIII metals as, e.g.,Group VIB metal oxides such as chromium, molybdenum and tungsten.Preferred complex metal silicate bases are those chrysotiles formed inwhole or in part of magnesium or aluminum, or both. Illustrative of suchbases are thin wall tubes and flakes of Mg (OI-I) Si O Preferably, thesurface area of the tubular shapes range from about 110 m lg to about250 m /g, and flakes range preferably from about 250 m /g to about 500 mlg and higher. Preferred materials of these types also are chrysotilescontaining from about 2 to about 10 weight percent aluminum, and acorresponding amount of magnesium as described by Formula II.

Preferred chrysotiles useful per se as aromatization catalysts are thosehigh surface area forms of thin wall tubes and flakes containing,besides magnesium, about 0.1 to 1 weight percent platinum, or from about1 to 15 weight percent chromium oxide (Cr O or from about 1 to 15 weightpercent molybdenum oxide (M00 or from about 1 to 15 weight percenttungsten, as the oxi e- E WFESEQ-B To illustrate useful catalysts foraromatization, a series of selected data are set out below. In oneinstance, chromia is composited with magnesium chrysotile and, inanother, platinum is composited with magnesium chrysotile to formaromatization catalysts. The chrysotile employed in each instanceconsists of flakes of 356 mlg, positively identified by X-raydiffraction data.

The chromia-magnesium chrysotile catalyst is prepared by dissolvingchromium oxide in water to form an aqueous solution, and then addingsame to the powdered magnesium chrysotile in amount sufficient to formpaste. The wetted powder is stirred to form a paste, the pastecontaining 15 weight percent chromium oxide on magnesium chrysotile. Thepaste is then heated in an oven at 150 C. for 16 hours. The dry mass isthen taken from the oven and crushed to a powder, and then calcined inair at 538 C. for 16 hours.

A portion of the catalyst composite is placed, as a fixed bed, in anupflow reactor and contacted at reaction conditions, as specified below,with a 50-95 C. cut of catalytic naphtha feed.

Feed composition, process conditions and the com- From these data it isclear that the aromatics concentration is increased at least 45 percent,the percent concentration of olefins and diolefins in the feeddecreasing in the product, while the concentration of alkyl benzenesincreases from a value of 4.02 percent in the feed to 5.83 percent inthe product.

In another demonstration, a 0.3 percent platinumon-magnesium chrysotilecatalyst is prepared by forming a paste by admixing the magnesiumchrysotile with an aqueous solution of chloroplatinic acid, drying samein an oven at 150 C. for 16 hours. The material is calcined at 1000.F.in air for 16 hours.

A portion of the catalyst composite is placed, as a fixed bed, in anupflow reactor and reduced in 1 atmosphere of H at 1000 F. Thetemperature is then lowered to 950 F. and the gas switched to N Thecatalyst is then contacted with a 50-95 C. cut of a cat naphtha feed.

Feed composition, process conditions and the composition of the effluentare tabulated below:

TABLE IV Process Conditions Temperature, C. 510

Pressure, psig 10 as N V/V/Hr.

Feed Liquid Product Composition, Composition,

Wt. Wt. Alkylbenzenes 4.02 7.70 Polycyclics 0.27 0.61 lsoparaffins 39.4437.21 n-Parafi'ins 1.20 7.00 Cyclic-C 10.92 12.78 Cyclic-C 0.04 0.00Olefins 30.40 26.40 Diolefins 13.70 8.30

From these data it is observed that the concentration of aromaticsincreases from 4.02 percent in the feed to 7.70 percent in the product,an increase of approximately percent.

Having described the invention, what is claimed is:

1. A process for the aromatization of olefin hydrocarbons comprisingcontacting feed streams containing olefinic hydrocarbons having fromabout 6 to about 12 carbon atoms, and higher, at temperatures rangingfrom about 300 C. to about 800 C., and pressures ranging from aboutatmospheric to about psi, with a catalyst comprising a chrysotile and atransition metal component selected from Group VIB and Group VIIImetals, of the Periodic Table of the Elements.

2. The process of claim 1 wherein the reaction is conducted attemperatures ranging from about 450 C. to about 550 C.

3. The process of claim 1 wherein the reaction is conducted at pressuresranging from atmospheric to about 75 psi.

4. The process of claim 1 wherein the chrysotile is in the physical formof tubes, and the surface area of the tubes ranges from about 1 10 m*/ gto about 250 m g.

5. The process of claim 1 wherein the chrysotile is in the physical formof flakes, and the surface area of the flakes ranges from about 250 m /gto about 500 m /g.

6. The process of claim 1 wherein the chrysotile component of thecatalyst composite contains from about 2 to about 10 wt. percentaluminum.

7. The process of claim 6 wherein the catalyst composite contains fromabout 0.1 to about 1 wt. percent platinum 8. The process of claim 6wherein the catalyst composite contains from about 1 to about 15 wt.percent molybdenum, as molybdenum oxide.

9. The process of claim 6 wherein the catalyst composite contains fromabout 1 to about 15 wt. percent tungsten, as the oxide.

10. The process of claim 6 wherein the catalyst composite contains fromabout 1 to about 15 wt. percent chromium, as the oxide.

2. The process of claim 1 wherein the reaction is conducted at temperatures ranging from about 450* C. to about 550* C.
 3. The process of claim 1 wherein the reaction is conducted at pressures ranging from atmospheric to about 75 psi.
 4. The process of claim 1 wherein the chrysotile is in the physical form of tubes, and the surface area of the tubes ranges from about 110 m2/g to about 250 m2/g.
 5. The process of claim 1 wherein the chrysotile is in the physical form of flakes, and the surface area of the flakes ranges from about 250 m2/g to about 500 m2/g.
 6. The process of claim 1 wherein the chrysotile component of the catalyst composite contains from about 2 to about 10 wt. percent aluminum.
 7. The process of claim 6 wherein the catalyst composite contains from about 0.1 to about 1 wt. percent platinum
 8. The process of claim 6 wherein the catalyst composite contains from about 1 to about 15 wt. percent molybdenum, as molybdenum oxide.
 9. The process of claim 6 wherein the catalyst composite contains from about 1 TO about 15 wt. percent tungsten, as the oxide.
 10. The process of claim 6 wherein the catalyst composite contains from about 1 to about 15 wt. percent chromium, as the oxide. 